Herbicide mixtures

ABSTRACT

The efficacy of defined aryloxypicolinamide herbicides, in particular their spectrum of weed control and selectivity for the crop species, is synergistically enhanced by combination with one or more selected second herbicidal compounds.

This application is a 371 of PCT/EP93/02737, filed on Oct. 5, 1993.

The present invention relates to an improvement in the efficacy ofaryloxypicolinamide herbicides by combination with a selected secondherbicidal compound.

Aryloxypicolinamides are a novel group of compounds, claimed inApplicants' European Patent No. 447004, which show excellent herbicidalactivity, in particular against broad leaf weeds in cereal crops.However, the aryloxypicolinamides when used as the sole activeingredient do not always achieve effective control of the full spectrumof weed species encountered in commercial agronomic practice, inconjunction with reliable selectivity for the crop species. Such gaps inthe spectrum of control can often be remedied by co-treatment withanother herbicide known to be effective against the relevant weedspecies. In the course of their investigations into the efficacy ofvarious partners for aryloxypicolinamides, Applicants have found thatselected combinations produce not merely the expected, additive effect,but exhibit a significant synergistic effect (i.e. these combinationsshow a much higher level of activity than predicted from that of theindividual compounds) which enables a greater selectivity for the cropspecies.

A mixture of herbicides shows a synergistic effect if the herbicidalactivity of the mixture is larger than sum of activities of theseparately applied compounds. The expected herbicidal activity for agiven mixture of two herbicides can be calculated as follows: (comp.Colby, S. R., "Calculating synergistic and antagonistic response ofherbicide combinations", Weeds 15, pp 20-22 (1967)): ##EQU1## Wherein Xis the percentage of growth inhibition upon treatment with a herbicide 1at a dosage of p kg/ha compared with an untreated control (X═0%)

Y is the percentage of growth inhibition upon treatment with a herbicide2 at a dosage of q kg/ha compared with an untreated control

WE. is the herbicidal effect to be expected upon treatment (% of growthinhibition compared with untreated control) with a combination ofherbicide 1 and 2 at a dosage of p+q g/ha

If the actual weed control (W) exceeds the expected (calculated) weedcontrol (WE), the mixture shows a synergistic effect.

Thus, the combinations of the present invention not only achieve controlof certain weed species which are difficult to combat effectively witharyloxypicolinamides alone, in particular grass weeds such as Alopecurusmyosuroides; Apera spica-venti; and Echinocloa crus-galli, but also showsignificant synergistic increase in the level of activity against thoseweeds and also many broad-leaved weeds. This combination of advantagesyields important benefits in practical agronomic applications. Firstly,it provides treatment for cereal crops which will control the majorityof the significant weed species; secondly it enables that effectivecontrol to be attained with lower application rates of activematerial--with consequential environmental benefits and also greaterselectivity of action in favour of the crop species.

Accordingly, the present invention provides a herbicidal compositioncomprising a herbicidally acceptable carrier and/or surface active agenttogether with, as active ingredient, a mixture of:

at least one aryloxypicolinamide of the general formula I ##STR1## inwhich Z represents an oxygen or sulphur atom;

R₁ represents a hydrogen or halogen atom or an alkyl or haloalkyl group;

R₂ represents a hydrogen atom or an alkyl group; q is 0 or 1;

R₃ represents a hydrogen atom or an alkyl or alkenyl group;

the or each group X independently represents a halogen atom or anoptionally substituted alkyl or alkoxy group, preferably a haloalkylgroup, or an alkenyloxy, cyano, carboxy, alkoxycarbonyl,(alkylthio)carbonyl, alkylcarbonyl, amido, alkylamido, nitro, alkylthio,haloalkylthio, alkenylthio, alkynylthio, alkylsulphinyl, alkylsulphonyl,alkyloximinoalkyl or alkenyloximinoalkyl group;

n is 0 or an integer from 1 to 5;

the or each group Y independently represents a halogen atom or an alkyl,nitro, cyano, haloalkyl, alkoxy or haloalkoxy group;

and m is 0 or an integer from 1 to 5;

together with a second herbicidal component selected from:

a) a urea-type herbicide, in particular chlortoluron, isoproturon,linuron or neburon;

b) a triazine-type herbicide in particular atrazine, cyanazine orsimazine;

c) a hydroxybenzonitrile herbicide in particular bromoxynil or ioxynil;and

d) an aryloxyalkanoic acid herbicide in particular dichlorprop.diclofop, MCPA or mecoprop (CMPP).

e) a dinitroaniline herbicide, such as pendimethalin;

f) a thiocarbamate herbicide, such as prosulfocarb;

g) amidosulfuron;

h) a diphenyl ether herbicide, such as aclonifen;

i) a pyridazine herbicide, such as pyridate;

j) a fluorene carboxylic acid herbicide, such as flurenol;

k) a pyridyloxyacetic acid herbicide, such as fluroxypyr;

l) an arylalanine herbicide, such as flamprop-isopropyl.

The pattern of persistence of the aryloxypicolinamide (abbreviatedherein as "AOP") is such that the combined treatment of the presentinvention can be attained either by the application of a preparedmixture as defined above, or by time separated application of separateformulations. Hence, in another embodiment, the present inventionprovides a method for controlling the growth of weeds at a cereal croplocus which comprises applying to the locus an AOP as defined in above,and a second component which is selected from those listed above.

The treatment according to the invention may be used to control a broadspectrum of weed species in cereal crops, e.g. wheat, barley, rice andmaize by pre- or postemergence treatment, especially early and latepost-emergence, without significant damage to the crop.

The term "pre-emergence application" means application to a soil inwhich seeds or seedlings are present before the emergence of the weedsabove the surface of the soil. "Post-emergence application" meansapplication to the aerial or exposed portions of the weeds which haveemerged above the surface of the soil.

Weeds that may be controlled by the combinations include:

    ______________________________________                                        Veronica persica                                                                           Veronica hedearaefolia                                                                       Stellaria media                                   Lamium purpureum                                                                           Lamium amplexicaule                                                                          Aphanes arvensis                                  Galium aparine                                                                             Alopecurus myosuroides                                                                       Matricaria inodora                                Matricarria matricoides                                                                    Anthemis arvensis                                                                            Papaver rhoeas                                    Poa annua    Apera spica-venti                                                                            Phalaris paradoxa                                 Phalaris minor                                                                             Avena fatua    Lolium perenne                                    Bromus sterilis                                                                            Poa trivialis  Spergula arvensis                                 Cerastes holosteoides                                                                      Arenaria seryllifolia                                                                        Silene vulgaris                                   Legousia hybrida                                                                           Geranium dissectum                                                                           Montia perfoliata                                 Myosotis arvensis                                                                          Chenopodium arvensis                                                                         Polygonum                                         Polygonum lapathifolium                                                                    Polygonum convolvulus                                                                        aviculare                                         Chrysantemum segetum                                                                       Centaurea cyanus                                                                             Galeopsis tetrahit                                Senecio vulgaris                                                                           Cirsium arvense                                                                              Viola arvensis                                    ______________________________________                                    

An exemplary compound for use as the aryloxypicolinamide component is ofthe general formula: ##STR2## wherein R₂ is a hydrogen atom or an ethylgroup, and Y is a hydrogen or fluorine atom.

The application rate of the AOP component is normally in the range of 25to 250 grams of active ingredient (gai) per hectare, with rates between30-100 gai/ha often achieving satisfactory control and selectivity. Theoptimal rate for a specific application will depend on the crop(s) undercultivation and the predominant species of infesting weed and canreadily be determined by established biological tests.

The selection of the second component will likewise be dependent on thecrop/weed situation to be treated, and will be readily identifiable bythose skilled in this area. The application rate of the second componentis determined primarily by the chemical type of that component, sincethe intrinsic activity of different types of herbicide varies widely.For example, the activity of a triazine herbicide, such as cyanazine orsimazine, can be almost tenfold greater than that of a urea herbicidesuch as chlortoluron or isoproturon. In general, the application rate ofthe second component is in the range of 500 to 5000 gai/ha, preferably1000-2500 gai/ha, when the second component is a urea or thiocarbamateherbicide; in the range 25 to 100 gai/ha when the second component isamidosulfuron or a pyridyloxyacetic acid herbicide; and in the range 100to 750 gai/ha when the second component is one of the other herbicidegroups listed above. Again, the optimal rate for the chosen secondcomponent will depend on the crop(s) under cultivation and the level ofweed infestation, and can readily be determined by establishedbiological tests. Naturally, with such a wide variation in applicationrate for the second component, the ratio of AOP to that second componentwill be determined predominantly by the choice of second component.Thus, the ratio AOP: Second Component may vary from 2:1 (secondcomponent=amidosulfuron) to 1:60 (second component=prosulfocarb).

I claim:
 1. Herbicidal composition comprising a herbicidally acceptablecarrier and/or surface active agent together with, as active ingredient,a herbicidally effective amount of a mixture of at least onearyloxypicolinamide (AOP) compound of the formula ##STR3## in which R₁represents a hydrogen or halogen atom or an alkyl or haloalkyl group;R₃represents a hydrogen atom or an alkyl or alkenyl group; each Xindependently represents a halogen atom or an optionally substitutedalkyl or alkoxy group, or an alkenyloxy, alkynyloxy, cyano, carboxy,alkoxycarbonyl, (alkylthio)carbonyl, alkylcarbonyl, amido, alkylamido,or nitro group; n is 0 or an integer from 1 to 5; each Y independentlyrepresents a halogen atom or an alkyl, nitro, cyano, haloalkyl, alkoxyor haloalkoxy group; and m is 0 or an integer from 1 to 5; together witha second component selected from the group consisting of:(a) a ureaherbicide; (b) a triazine herbicide; (c) a hydroxybenzonitrileherbicide; (d) an aryloxyalkanoic acid herbicide; (e) a dinitroanilineherbicide; (f) a thiocarbamate herbicide; (g) amidosulfuron; (h) adiphenyl ether herbicide; (i) a pyridazine herbicide; (j) a fluorenecarboxylic acid herbicide; (k) a pyridyloxyacetic acid herbicide; and(l) an arylalanine herbicide wherein the weight ratio of AOP to saidsecond component in said composition ranges from 2:1 to 1:60. 2.Composition as claimed in claim 1 wherein the second component isselected from the group consisting of chlortoluron, isoproturon,cyanazine, bromoxynil, ioxynil, dichloroprop, diclofop, MCPA, mecoprop(CMPP), pendimethalin, prosulfocarb, amidosulfuron, aclonifen, pyridate,flurenol, fluroxypyr, and flamprop-isopropyl.
 3. Composition as claimedin claim 1 wherein said second component is a urea or thiocarbamateherbicide and the ratio of AOP to said second component is 1:10 to 1:60.4. Composition as claimed in claim 1 wherein said second component isamidosulfuron or a pyridyloxyacetic acid and the ratio of AOP to saidsecond component is 2:1 to 1:20.
 5. Composition as claimed in claim 1wherein said AOP compound has the formula: ##STR4##
 6. Composition asclaimed in claim 1 wherein X is haloalkyl.
 7. Composition as claimed inclaim 5 wherein X is haloalkyl.
 8. Composition as claimed in claim 7wherein X is CF₃.
 9. Method of controlling the growth of weeds at acereal locus which comprises applying to the locus an effective amountof the herbicidal composition of claim
 1. 10. Method as claimed in claim9 wherein the AOP is applied to the locus at a rate of 25 to 250 gai/ha.11. Method as claimed in claim 9 wherein the second component is a ureaor thiocarbamate herbicide and is applied to the locus at the rate of1000-2500 gai/ha.
 12. Method as claimed in claim 9 wherein the secondcomponent is amidosulfuron or a pyridyloxyacetic acid herbicide and isapplied to the locus at the rate of 25 to 100 gai/ha.
 13. Method asclaimed in claim 9 wherein said AOP compound is ##STR5## where X ishaloalkyl.
 14. Method as claimed in claim 13 wherein X is CF₃.
 15. Aherbicidal composition comprising a herbicidally acceptable carrierand/or surface active agent together with, as active ingredient, aherbicidally effective amount of a mixture of at least onearyloxypicolinamide (AOP) compound of formula: ##STR6## wherein R³represents a hydrogen atom or an alkyl group; X represents a haloalkylgroup;R₁ represents a hydrogen or halogen atom or an alkyl or haloalkylgroup; Y represents a halogen atom; and m is 0 to 1; together with asecond component selected from the group consisting of chlortoluron,isoproturon, cyanazine, bromoxynil, ioxynil, dichlorprop, diclofop,MCPA, mecoprop (CMPP), pendimethalin, prosulfocarb, amidosulfuron,aclonifen, pyridate, flurenol, fluroxypyr and flamprop-isopropyl,wherein the weight ratio of AOP to the second component is 2:1 to 1:60.16. Composition as claimed in claim 15, wherein the weight ratio of AOPto said second component is from 1:2 to 1:60.
 17. Composition as claimedin claim 15, wherein the weight ratio of AOP to said second embodimentis from 1:10 to 1:60.
 18. Composition as claimed in claim 15 whereinsaid AOP compound has the formula: ##STR7##
 19. Composition as claimedin claim 15 wherein X is haloalkyl.
 20. Composition as claimed in claim18 wherein X is haloalkyl.
 21. Composition as claimed in claim 20wherein X is CF₃.
 22. Method of controlling the growth of weeds at acereal locus which comprises applying to the locus an effective amountof the herbicidal composition of claim
 15. 23. Method as claimed inclaim 22 wherein said AOP compound is ##STR8## where X is haloalkyl. 24.Method as claimed in claim 23 where X is CF₃.